Poor correlation between large-scale environmental flow violations and freshwater biodiversity: implications for water resource management and the freshwater planetary boundary

[摘要] The freshwater ecosystems around the world are degrading, such thatmaintaining environmental flow 1 (EF) in rivernetworks is critical to their preservation. The relationship betweenstreamflow alterations (subsequent EF violations 2 ) and the freshwater biodiversity response is well established at the scale of stream reaches or small basins ( ∼ 100  km 2 ). However, it is unclear if this relationship is robust at larger scales, even though there are large-scale initiatives to legalize the EF requirement. Moreover, EFs have been used in assessing a planetary boundary 3 for freshwater. Therefore, this study intends to conduct anexploratory evaluation of the relationship between EF violation andfreshwater biodiversity at globally aggregated scales and for freshwaterecoregions. Four EF violation indices (severity, frequency, probability ofshifting to a violated state, and probability of staying violated) and sevenindependent freshwater biodiversity indicators (calculated from observedbiota data) were used for correlation analysis. No statistically significant negative relationship between EF violation and freshwater biodiversity was found at global or ecoregion scales. These findings imply the need for a holistic bio-geo-hydro-physical approach in determining the environmental flows. While our results thus suggest that streamflow and EF may not be the only determinant of freshwater biodiversity at large scales, they do not preclude the existence of relationships at smaller scales or with more holistic EF methods (e.g., including water temperature, water quality, intermittency, connectivity, etc.) or with other biodiversity data or metrics.

[学科分类] 妇产科学